The present invention relates to the manufacture of gate valve assemblies of the sliding or rotary type for closure devices having a pouring nozzle, e.g., a molten metal ladle or tundish. Customarily, these assemblies are comprised of a plurality of slabs of refractory bricks pierced by a hole and designed to slide or rotate with respect to each other in order to allow steel or pig iron to flow from a casting ladle or, on the contrary, stop the flow. As understood in the art, the upper plate assembly is generally stationary while the lower plate assembly slides or rotates against the upper plate assembly. As used herein, the term "gate valve assembly" is intended to mean either the upper plate assembly or the lower plate assembly.
The manufacture of these gate valve assemblies generally requires the use of special refractory products resistant to the erosion of the flowing molten metal and to thermal shock, a precise assembly of the bricks comprising them, and machining of the sliding faces so as to avoid leakage of metal. As known in the art, these sliding or rotary gate valve assemblies are formed from a plurality of preformed pieces of refractory material which are assembled, generally with a heat settable cement. The refractory material which will contact the molten metal is formed from high temperature fired, erosion resistant refractory material although the backup refractory may be castable. See for example, U.S. Pat. Nos. 3,926,406; 3,970,283; and 4,063,668. It will be apparent that the above-mentioned method of manufacturing gate valve assemblies involves considerable amounts of hand labor and is an expensive method for producing these valves.
It has recently been suggested in published French Patent Application Nos. 77/01683 and 77/19344 that an integral slide gate and nozzle assembly can be made by casting a refractory concrete into a metal envelope and allowing the concrete to harden within the envelope. Vibrating of the envelope to compact the concrete is disclosed in the former application. Neither of these applications disclose forming the assembly in a manner which obviates the need for further machining of the upper surface of the assembly to provide a suitably flat sliding surface.
The present invention makes it possible to manufacture gate valve assemblies more economically than before, regardless of their form, by eliminating the need to machine the sliding surface and by obviating any special care in assembly of the pieces used to form the assemblies.